This invention pertains to a method and apparatus for more effectively conducting various metal cutting operations with a gun drill and, more particularly, to providing improved seal means reducing bearing failure when operating such apparatus.
Gun drill apparatus of various types have been employed for a considerable time period to carry out various metal cutting operations including the drilling of holes, reaming, chamfering, counterboring and the like. A typical apparatus of this type is described in U.S. Pat. No. 3,361,014 comprising a drill tube formed by a rod having a longitudinal V groove or flute in one side thereof and a drill head, similar in cross sectional configuration to that of the drill rod and slightly larger in diameter which is formed at one end of the drill rod. This configuration is said to provide cutting edges and a passage through which chips may be washed from the workpiece by lubricant fed into the bore with a central passage through the drill rod. Such gun drill is further reported to employ a chip box in connection with the machining operation having one end wall against the face of the workpiece for receiving the chips and lubricant from the drill work and with the opposite end wall having an opening through which the drill rod extends when conducting the selected machining operation. A guide member is further disclosed in said prior art patent for rotatably mounting the gun drill rod in a supported bearing structure with said guide member having a resilient body with an opening therein for receiving the gun drill rod with the opening corresponding in configuration to the drill rod in having normal dimensions slightly smaller than the drill member. The disclosed guide member is said to comprise a cylindrical body of resilient plastic material adapted to be received inside the inner race of an anti-friction bearing and having an irregular central opening therethrough corresponding in form to the cross sectional form of the gun drill rod whereby said gun drill rod may be extended therethrough, the ends of the cylindrical body having radially extending flanges, one of which provides a relatively extensive sealing surface abutting one end face of the anti-friction bearing in which the body is received with the remaining flange at the other end being of substantially less diameter than the first mentioned flange and forming an abutment which engages the opposite end face of the bearing to retain the body inside the bearing race and which flange is deformable to permit insertion thereof through the race for installing or removing the body from the bearing. The particular gun drill apparatus therein disclosed employs a horizontal drill spindle having a chuck thereon for receiving the shank end of the gun drill rod in the usual manner. The spindle moves toward and from the workpiece to advance the drill into the cut bore and to remove it from the workpiece as is well understood in the art. A suitable lubricant is pumped through a passage in the spindle member which further proceeds through an internal passageway formed in the drill rod for lubrication and cooling the workpiece being drilled. The particular guide assembly further therein disclosed is said to be positioned in one end wall of the chip box opposite the end wall having an opening through which the drill rod extends.
A generally similar gun drill apparatus is also disclosed in U.S. Pat. No. 3,606,560 which features modified lubrication passageways being formed in the drill rod member but which is said to correspond to the above described apparatus in other respects. The guide assembly said therein to be employed is expressly said to be that described in U.S. Pat. No. 3,361,014 wherein the radial flanges provided in the resilient guide member at opposite ends do not extend beyond the cooperating bearing device. It has now been found that a more effective seal is needed for such guide assemblies to avert serious damage to the associated bearing when contacted with metal chips and particles formed from the workpiece. In providing more effective sealing of the bearing means in such guide assemblies it becomes further advantageous to do so by means affording still better protection to the plastic guide member itself from wear caused by these abrasive substances. It would be still further advantageous in affording such greater protection to the plastic guide member itself that the means employed also protect against erosion from the heated lubricant or coolant impinging thereon.
It is an object of the present invention, therefore, to provide an improved gun drill apparatus less susceptible to bearing failure caused by customarily encountered operating conditions.
It is another object of the present invention to provide an improved guide assembly for a gun drill apparatus to include more effective seal protection of the cooperating bearing means.
A still further object of the present invention is to provide improved guide means for a gun drill rotatably mounted in a supported bearing structure which more effectively seals the bearing device from abrasive wear while also affording protection against heated lubricant erosion.
Still another object of the present invention is to provide a method for operation of a gun drill apparatus which reduces bearing failure.
These and still other objects of the present invention will become apparent upon considering the following detailed description for the present invention.